Influence of ecologically relevant urea fertilizer concentrations on nematodes: A microcosm experiment

Aim of study: Urea remains one of the most widely used chemical fertilisers in the world and is used extensively in the Philippines as a major source of nitrogen for crops. However, we have a very limited understanding of its impact on soil fauna such as nematodes. In this study, we demonstrated the suitability of the microcosm set-up to assess chemical effects on nematode communities under controlled conditions and determined the effects of urea on nematode communities. Area of study: The soil samples were obtained from a relatively “less disturbed” field in Bukidnon, Central Mindanao and were taken for experimentation in a greenhouse at Premier Research Institute of Science and Mathematics (PRISM), Mindanao State University - Iligan Institute of Technology (MSU-IIT), Iligan City, Philippines. Material and Methods: The soil was collected and analysed for its physiological properties. The soil was then exposed to urea concentrations (0 mg/kg, 19.67 mg/kg, 39.33 mg/kg and 78.66 mg/kg) in a microcosm for 45 days. Nematodes were then collected and processed using a modified dish method. Main results: Firstly, the natural microcosms (without urea) showed that nematode abundance and the number of genera decreased by 28% and 35%, respectively. The results suggest that the current microcosm setup may still be useful in testing the effects of certain chemicals of interest. Secondly, no significant effects on the number of genera and diversity indices were observed with urea, except on the day 15 when nematode abundance was significantly higher at 39.33 mg/kg than at 19.67 mg/kg. Research highlights: This study shows that the above ecologically relevant urea concentrations had no negative impact on nematode community structure during the 45-day exposure.